U.S. patent application number 11/953441 was filed with the patent office on 2008-06-12 for method for treating metallic surfaces with an alternating electrical current.
This patent application is currently assigned to ELISHA HOLDING, LLC. Invention is credited to William Dalton, Wayne Soucie, Dennis Winn.
Application Number | 20080135135 11/953441 |
Document ID | / |
Family ID | 39512429 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080135135 |
Kind Code |
A1 |
Soucie; Wayne ; et
al. |
June 12, 2008 |
Method For Treating Metallic Surfaces With an Alternating
Electrical Current
Abstract
A method for providing enhanced corrosion protection of metallic
components and surfaces when exposing the metallic component to a
silicate medium while applying an AC (Alternating Current)
current.
Inventors: |
Soucie; Wayne; (Columbia,
MO) ; Winn; Dennis; (Moberly, MO) ; Dalton;
William; (Moberly, MO) |
Correspondence
Address: |
POLSTER, LIEDER, WOODRUFF & LUCCHESI
12412 POWERSCOURT DRIVE SUITE 200
ST. LOUIS
MO
63131-3615
US
|
Assignee: |
ELISHA HOLDING, LLC
Moberly
MO
|
Family ID: |
39512429 |
Appl. No.: |
11/953441 |
Filed: |
December 10, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60874165 |
Dec 11, 2006 |
|
|
|
Current U.S.
Class: |
148/241 |
Current CPC
Class: |
C25D 9/04 20130101 |
Class at
Publication: |
148/241 |
International
Class: |
C23C 8/00 20060101
C23C008/00 |
Claims
1) A method for treating a metallic surface comprising: contacting
a metallic surface with a medium comprising at least one silicate,
and; providing an alternating current to the medium for a time and
under conditions sufficient to improve the corrosion resistance of
the metallic surface.
2) The method of claim 1 wherein the silicate comprises sodium
silicate.
3) The method of claim 1 wherein the medium comprises water and at
least one silicate.
4) The method of claim 1 wherein the metallic surface comprises at
least one member selected from the group consisting of zinc, zinc
nickel, tin zinc, and zinc iron.
5) The method of claim 1 wherein the providing comprises contacting
the metallic surface with an alternating current while the metallic
surface is at least partially in contact with the medium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
application No. 60/874,165, filed Dec. 11, 2006, and which is
incorporated herein by reference.
[0002] Additionally, the subject matter of the instant invention is
related to the following patents and patent applications: U.S. Pat.
Nos. 6,149,794; 6,258,243; 6,153,080; 6,322,687; 6,572,756B2;
6,592,738B2; 6,599,643; 6,761,934; 6,753,039; 6,866,896B2; Ser.
Nos. 10/211,094; 10/636,904; 10/713,480; and 10/831,581. The
applications have been published as Publication Nos. 20030209290,
20050031894, 20040137239 and 20040222105, respectively. The
disclosure of the foregoing patents and patent applications are
hereby incorporated by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] Not Applicable.
FIELD OF THE INVENTION
[0004] Enhanced corrosion protection for metallic components and
surfaces using a silicate based solution where AC (Alternating
Current) current is applied.
BACKGROUND OF THE INVENTION
[0005] The development and use of silicates as process solutions
for electroless, electrolytic (cathodic or anodic) environments are
known. The resulting layer from electroless processes tends to be
relatively soluble unless a reducing agent is added. DC (Direct
Current) processes where the work piece is the cathode or the anode
are dependent upon the substrate and or the type of chemistry
involved. Typically DC processes are used to the extent that a
favorable reaction takes place on the surface based upon whether or
not the reaction requires that electrons be contributed to the
resulting layer or given up by the surface. Pulse processing has
been demonstrated to facilitate some processes such as chrome
plating where efficiency can be increased by repeatedly breaking
down the cathodic film, which buildup on the surface that is being
plated. In pulse processes the work piece is still net cathodic or
anodic based upon the chemistry or surface being deposited.
[0006] Prior art processes have employed electrolytic cathodic
process to deposit a beneficial layer with improved corrosion
resistance on zinc, zinc alloy plated substrates and zinc diecast
components. First the deposition of Silicon is not inherently
cathodic in nature. Therefore, without wishing to be bound by any
theory or explanation, it is believed that the resulting layer is
the result of the pH environment created by the cathodic polarity
of the surface, not the direct reduction on the surface due to the
availability of electrons. In addition, in a DC process there is a
companion reaction, which occurs at the anode. This companion
reaction may facilitate the beneficial result and in typical Zinc
plating where the Zinc+ ions required for plating can be
electrically oxidized at the anode for electro-reduction to zinc
metal at the cathode. There is a need in this art for an
electrolytic process for treating a metallic surface with silicates
in order to improve the corrosion resistance of the metallic
surface.
BRIEF SUMMARY OF THE INVENTION
[0007] Briefly stated, a method for treating a metallic surface is
disclosed. The method comprises contacting a metallic surface with
a medium comprising at least one silicate and providing an
alternating current to the medium for a time and under conditions
sufficient to improve the corrosion resistance of the metallic
surface. The silicate can be sodium silicate. The medium can
comprise water and at least one silicate. The metallic surface can
comprise at least one member selected from the group consisting of
zinc, zinc nickel, tin zinc, and zinc iron. In accordance with one
aspect of the method, the step of providing the alternating current
to the medium comprises contacting the metallic surface with an
alternating current while the metallic surface is at least
partially in contact with the medium.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0008] FIG. 1 is a schematic of the apparatus and electrical system
that can be used in an AC method of the invention.
[0009] FIG. 2 is a graphical representation of the corrosion
resistance of articles treated in accordance with the
invention.
[0010] Corresponding reference numerals will be used throughout the
several figures of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The following detailed description illustrates the invention
by way of example and not by way of limitation. This description
will clearly enable one skilled in the art to make and use the
invention, and describes several embodiments, adaptations,
variations, alternatives and uses of the invention, including what
I presently believe is the best mode of carrying out the invention.
Additionally, it is to be understood that the invention is not
limited in its application to the details of construction and the
arrangements of components set forth in the following description
or illustrated in the drawings. The invention is capable of other
embodiments and of being practiced or being carried out in various
ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting.
[0012] The instant invention relates to using AC current to treat a
metallic surface (e.g., to provide the opportunity for all
beneficial reactions based upon polarity to occur on the work
piece) in a silicate containing medium. The metallic surface can
comprise an electroplated article (e.g., a zinc plated fastener),
discrete components having a metallic surface, metallic or metallic
coated sheets or rolls, among other surfaces. The silicate
containing medium can comprise water, at least one silicate, and
optionally additives such as silica. An example of a suitable
silicate comprises sodium silicate.
[0013] Experiments using AC current instead of DC have demonstrated
an improvement in corrosion performance in ASTM-B-117 corrosion
testing. Data collected indicates that an increase in hours to 1st
white corrosion of 144% (52 to 127) and an 80% increase in the
average time to 5% red failure. Samples for this evaluation came
from the same Zinc plating batch. The cathodic process using a
sodium silicate solution, process times, process temperature, dry
conditions, and current densities in accordance with the previously
identified Cross-Referenced Patents and Applications were
constants. The processes disclosed therein are incorporated herein
by reference. The DC cathodic samples were processed using
conventional process equipment. The AC samples were produced using
an opposed barrel configuration illustrated in FIG. 1.
[0014] An experiment wherein the initial current density was
tripled yielded an increase in average time to 1st white corrosion
of 469%. At 480 hours of exposure only 1 sample out of 20 has
reached 5% red rust, whereas all 20 samples from the conventional
DC process had failed by 240 hours of exposure.
[0015] The AC process has the advantages of: 1) no dimensionally
stable anode is required and thereby minimizes capital costs for
setting up the process, and 2) in this configuration work pieces
comprise both sides of the electrical circuit; therefore time
efficiency is increased in that finished parts can be processed
simultaneously.
[0016] The electrical dynamics of AC current are different than the
use of pulse rectifiers in that typical pulse sources generate
waveforms similar to square waves. In this condition voltage
transitions are extremely rapid to a set threshold and remain at
the predefined level until rapidly changed again. Conventional AC
current is constantly undergoing changes in voltage and current
relationships, which can potentially change the chemical response
at the surface of the work piece.
[0017] If desired, after exposure to the AC environment, the
exposed metallic surface can be rinsed and dried. In some cases,
the exposed metallic surface is coated with a film or layer in
order to impart improved corrosion resistance, color, and
lubricity, among other properties. Examples of suitable coatings
can comprise at least one member selected from the group consisting
of latex, epoxy, acrylics, and urethanes, among other coatings.
[0018] The configuration of FIG. 1. shows the physical components
and electrical configuration of the inventive process. A barrel
process is shown, however, a rack process could utilize a similar
electrical circuit.
[0019] The following Examples are provided to illustrate certain
aspects of the invention and do not limit the scope of the appended
claims.
EXAMPLES
[0020] Zinc plated rivets were treated in accordance with the
following Examples.
[0021] Medium/Solution: 9.8% Sodium Silicate in de-ionized
Water
[0022] Temperature: 149.degree. F. (65.degree. C.)
[0023] Time 7.5 min
[0024] Barrel size (2) Lusteron 2''.times.4''
[0025] Rotation; nominal 12 RPM
Example 1
[0026] (Corrosion Test--Group 1) Voltage to achieve 2.0 nominal
amps 14 VAC
[0027] Current trend. 0 min. 2.9-3.0 amps, 3.5 min. 0.9-1.5 amps,
5.0 min. 0.8-1.0 amps, 7.5 min. 0.8-0.9 amps.
[0028] Rivet appearance shiny
Example 2
[0029] (Corrosion Test--Group 2) 10 amp target could not be reached
stopped increasing voltage at 50 VAC
[0030] As voltage was increased a new short term peak could be
reached then would diminish.
[0031] Current trend 0 min. 6-9 amps, 1 min. 3-4 amps, 3 min.
2.5-4.0 amps, 5 min. 1.5-3.0 amps.
[0032] Arcing visible inside barrels, Run terminated at 5 minutes
after an arcing event. Continuity testing on the barrel danglers
indicated infinite resistance.
[0033] Sanded dangler ends to remove buildup continuity
restored
[0034] Dangler in neutral barrel black
[0035] Dangler in L1 barrel amber color
[0036] Rivet appearance dull gray.
Example 3
[0037] (Corrosion Test--Group 3) Voltage to achieve target 0.6 amps
2 VAC
[0038] Current trend 0 min. 0.6 amps, 1.5 min. 0.4-0.6 amps, 4 min.
0.3-0.6 amps, 7.5 min. 0.3-0.7 amps.
[0039] Rivet appearance shiny
[0040] The following Table summarizes the corrosion resistance of
the Group of rivets when measured in accordance with ASTM B-117.
FIG. 2 is a graphical representation of the corrosion resistance of
these Groups.
TABLE-US-00001 Part Time Group Group Description Type Part. No.
Area N n Min Avg n Min Avg n Min Avg (hours) Group 01 Zinc(AC)EMC
Rivets 99020033 Main 20 20 72 127 19 192 289 19 216 322 648 AC
Process 2 amps 7.5 min. D/R/D Group 02 Zinc(AC)EMC Rivets 99020033
Main 20 17 96 315 3 384 520 3 432 560 648 AC Process 6 amps 7.5
min. D/R/D Group 03 Zinc(AC)EMC Rivets 99020033 Main 20 20 24 104
20 144 253 20 144 276 504 AC Process 0.6 amps 7.5 min. D/R/D Group
04 Zinc Typical Rivets 99020033 Main 20 20 24 52 20 120 157 20 144
172 240 DC Process Line #3 EMC 22 amps 7.5 D/R/D
[0041] In view of the above, it will be seen that the several
objects and advantages of the present invention have been achieved
and other advantageous results have been obtained.
[0042] As various changes could be made in the above constructions
without departing from the scope of the invention, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *